Abstract [en]

The purpose of the project was to investigate whether the use of slag asphalt in urban and high traffic areas can reduce dust problems during the winter. Wear measurements in PVM presents an unclear picture. Test of particle formation and wear characteristics have been performed in the Road Simulator at VTI on a SMA8 pavement with slag from Ovako Bar. Although an earlier test in the road simulator (PVM) on an SMA11 pavement with the same slag materials are included in this report. Wear measurements in PVM presents an unclear picture probably because of the slag used contained more steel residues than normal slag, resulting in a very uneven surface with protruding sharp steel pieces after some wear of the surface, which in turn led to increased stud protrusion during measurement and the increased wear of the pavement surface. In tests with conventional asphalt stud protrusion is reduced under wear test. It is therefore very difficult to compare the wear measurement on this slag asphalt with results from previous runs on other types of asphalt wearing courses. Because of the unclear development of wear the overriding aim of the investigations could not really be achieved. Wear properties of the SMA8 with slag tested according to the ‘Prall’-method (EN 12697-16) show very high/good abrasion resistance. The tests in the road simulator has also shown that particle formation from SMA8 slag asphalt, measured as PM10, is at the same level as previously tested SMA11 with slag and at similar level than most asphalt wearing courses made from natural aggregates. The particle mass is dominated by particles at two modes, 3 and 6 µm, while the number concentration is dominated by ultrafines at about 20 nm. SMA8 with slag give rise to a much lower number concentration of ultrafines at about 20 nm than the previously tested asphalt pavements and previously tested SMA11 with slag. Element analysis of PM10 shows a distribution very similar to that of the previously tested slag pavement in 2013. Ca, Fe and Si are principal elements in the size fraction 1–10 µm, followed by Al, Mn, Cr and K. Scanning electron microscopy reveals that PM10 particles have angular, grainy and flaky shapes as well as some needle shaped and exhibit typical features of mineral and metallic fragments. Particles down to a couple of 100 nm were observed in the SEM pictures.